U.S. Pat. No. 5,902,535 describes an inner mould line (IML) tool for resin film infusion moulding a component in a single-step moulding operation. The IML tool comprises a plurality of mandrels in a modular design. The mandrels may be individually assembled over a preform assembly, such that the surface configurations on the underside of the mandrels match with the stringers and intercostals of the preform assembly.